Digi 002 makes noise @ low buffer settings

[gvees]

Hi y'all..

I bought a Digi 002 a while ago and had it repaired at an ARC because the firewire ports were blown and the PSU was in bad shape.. Anyhow, I now finally have it and was running some primary testruns and I noticed a number of things I really don't like...

The most important thing is that when I run it at low buffer settings (256, 128, 64) it generates noise. There's a high pitched squeal a long with random (jitter like) noise. it stutters every now and than and the pitch gets higher as i lower the buffer settings or when I change the sample rate. The noise gets less when I have it on a buffer of 512, but it's still there with my ears in front of the speaker. At the lower buffer settings it is pretty loud and very (!) annoying...

If anyone has any opinions or thoughts that could help me work this noise out of my studio I'd be very grateful!

Before I had the 002 I worked with an Mbox 2 and didn't have any noise at all! I use the same cables I did with the Mbox...

[TOM@METRO]

What firewire controller are you using? Have you tried changing firewire ports and cables?

[gvees]

I use the onboard firewire controller of my Gigabyte motherboard, which has a Texas Instruments TSB43AB23 chip controller

I haven't tried any different firewire cables, I only have one.. Could that be the problem? I'll have to get a new cable than...

[sunburst79]

Hi gvees, I would try it on another computer if you can. This would be the simplest method of testing it.

I would be leaning towards some sort of ground loop type issue. There have been all sorts of posts over the years involving noises going away when switching to from unbalanced to balanced speaker connections etc. Try disconnecting everything but the 002 and a pair of headphones and make sure the 002 and computer are plugged into the same outlet, UPS power strip etc if at all possible in order to minimize the chance of a mains related issue.

The TI FW chips are usually good with PT but if your had a way to check it with another Digi FW interface like a 003 or MBox2 Pro it would tell you a lot in regards to the actual controller chip on the motherboard. Inserting a know good PT approved PCI FW card adapter (and possibly disabling the onboard FW in BIOS) would do the same thing.

Bad 002 or bad repair... It can happen. Most reports are that Digis service is quite good but something may have got missed or not been acting up while on the test bench the day your 002 was being worked on. I know there is a separate FW controller board in the 002 but I dont know what behavior they take when failing. I think normally they just die and the 1394 link LED remains dark.

I would try the isolating the 002 electrically as my first step, try the 002 on another computer as my second step and the FW card as my third but that will depend on what you have to test with.

Best luck

[gvees]

Thanks! I already have the 002 connected to a clean power source (I've made a special electric 'group' that only serves my studio) so that shouldn't be the problem..

Can it also be a ground loop issue when the noise randomly interrupts every now and then? The noise also changes when I select different sample rates and H/W Buffer settings... It's worst at 48kHz @ 64 buffer..

Also it outputs a high pitch which gives a constant signal flow on the signal leds of my amplifier when PT isn't running but I only have the 002 powered on..

I didn't have any issues with my previous Mbox 2 (USB), does that help?

[sunburst79]

Originally Posted by gvees

Thanks! I already have the 002 connected to a clean power source (I've made a special electric 'group' that only serves my studio) so that shouldn't be the problem.

Good.

Can it also be a ground loop issue when the noise randomly interrupts every now and then? The noise also changes when I select different sample rates and H/W Buffer settings... It's worst at 48kHz @ 64 buffer.

Probably not a ground loop. The fact that it changes with the buffer size tends to make me think its related to the Firewire chip or FW board in the 002. Have you tried a substituting a known good FW cable?

The paradox here is that you make no mention of DAE errors so I assume PT itself is running okay without a large number of unexpected errors? If thats the case it points to the FW chip/controller board working fine. Although the noise may be some type of component breakdown thats letting digital grit or clock noise or some other type of electrical interference into the audio signal path. Do you have the 002s clock set to internal. You should.

Also it outputs a high pitch which gives a constant signal flow on the signal leds of my amplifier when PT isn't running but I only have the 002 powered on.

But have you unplugged everything but the 002 and a pair of headphones? Computer>002> Headphones....Turn off the amp, unplug any MIDI Cables, external drives etc. The idea here is to electrically isolate everything but the computer, the FW cable and the 002

I didn't have any issues with my previous Mbox 2 (USB), does that help?

Ah but your MBox2 was USB.....I'm reading it as the MBox2 worked fine with the current monitoring system, Speakers, Amps, Cables? Nothings changed but the interface?

[gvees]

Originally Posted by sunburst79

Good.

:)

Probably not a ground loop. The fact that it changes with the buffer size tends to make me think its related to the Firewire chip or FW board in the 002. Have you tried a substituting a known good FW cable?

yup, plugged in a brandnew firewire cable this morning, same problem..

The paradox here is that you make no mention of DAE errors so I assume PT itself is running okay without a large number of unexpected errors? If thats the case it points to the FW chip/controller board working fine. Although the noise may be some type of component breakdown thats letting digital grit or clock noise or some other type of electrical interference into the audio signal path. Do you have the 002s clock set to internal. You should.

I do have some buffer problems but that's more likely to be caused by unoptimised windows.. PT is running pretty okay..
I've just reinstalled XP because I was working on Win7 that didn't like the 002.. :P

But have you unplugged everything but the 002 and a pair of headphones? Computer>002> Headphones....Turn off the amp, unplug any MIDI Cables, external drives etc. The idea here is to electrically isolate everything but the computer, the FW cable and the 002

Hmm.. Headphone is only mono... that's no good, but in any case, no hiss, squeaks or noise on headphones... (with only the absolute necessary connections i.e. firewire and ac cord)

Ah but your MBox2 was USB.....I'm reading it as the MBox2 worked fine with the current monitoring system, Speakers, Amps, Cables? Nothings changed but the interface?

correct!

[sunburst79]

Originally Posted by gvees

:)

yup, plugged in a brandnew firewire cable this morning, same problem..

I do have some buffer problems but that's more likely to be caused by unoptimised windows.. PT is running pretty okay..
I've just reinstalled XP because I was working on Win7 that didn't like the 002.. :P

Hmm.. Headphone is only mono... that's no good, but in any case, no hiss, squeaks or noise on headphones... (with only the absolute necessary connections i.e. firewire and ac cord)

correct!

You might try optimizing Windows and seeing if the buffer errors go away. Its possible that the FW is working well enough most of the time but is having some issues.

Juice=Good
FW Cable=Good
Monitor System= Good I think we can say that since they are working with the MBox.

Unknown=the 002 FW controller board and the FW chip on the motherboard

A Digi approved FW card to test with would come in handy right now

One other thing to try would be attempting to roll back the FW driver from "Texas Instruments OHCI Open Host Controller" to "OHCI Compliant IEEE Host Controller" in the Update Driver dialog of Hardware Manager.

Short of trying the 002 on another computer or dropping in a Digi approved FW card I'm kinda running out of suggestions.

[gvees]

thanks! I'll give it a try and see if I can get a different pc or firewire card to try..!

If that doesn't work I'll have to send it back to the repair center...

[gvees]

One step further.. I've just connected my 002 with a balanced cable (didn't have that before, but with the Mbox it didn't give any problems) but it doesn't make any difference..

So no noise on the headphone outputs, but a lot of noise on the regular outputs when running Pro Tools at sample rates lower than 1024. At 1024 there's also noise but such a high pitch you hardly notice it.. (Still it's not right..)

I wonder if there's a Digi Tech guy who could chime in? Otherwise I'll contact the repair center again...